It Came From Beneath the Sea (1955)

The models are smaller in this early Harryhausen project; it shows, but the
stop motion animation still works well enough. Most of the creature effects
are in the last 20 minutes and the final conflict is a bit
anticlimactic. Unlike other monster films we don't have a lot of sympathy for
the creature this time. Cephalopods, like big bugs, are beyond the limit.

We have more than the usual romantic development between the submarine captain
and brainy marine biologist. As a kid I thought Kenneth Tobey and Faith
Domergue were major stars because they appeared in several 50s SF films. These
were important roles!

The San Francisco locations were shot surreptitiously because the city fathers
would not give permission, fearing that people would lose confidence in the
Golden Gate Bridge should it be attacked by a giant radioactive six-tentacled
octopus.

They have a real octopus in a lab scene; I never noticed before how graceful
and cinematic they are when underwater.

Available on Blu-ray with b&w and colorized versions switchable with the Angle
button. It has the usual appreciative commentary track with Harryhausen and
admirers.